Electronic control system for the injectors of internal engines

ABSTRACT

An electronic circuit system for triggering the successive injectors of an internal combustion engine, chiefly a Diesel engine. A first circuit controlled by the rotation of the engine provides for the starting of saw-tooth voltage wave, the length of the rising slope of which depends on the speed of rotation while the peals of said pulses trigger the injections which last until the end of the pulse. A delay for said triggering is advantageously obtained by the difference between the time constants of two flip-flops the first of which is constant while that of the second flip-flop depends on the operative parameters of the engine, the end of the injection being defined by the end of the signal produced by the first flip-flop.

United States Patent [151 3,653,365- Monpetit 1 Apr. 4, 1972 [54]ELECTRONIC CONTROL SYSTEM FOR [56} References Cited THE INJECTORS OFINTERNAL UNITED STATES PATENTS ENGINES v 2,644,094 6/1953 Douglas 123/32 EA Inventor: Louis A. Monpetit, LEtang-La-Ville,

France Assignee: Societe des Procedes Moderness dlnjection Sopromi, LesMureaux, France Filed: Mar. 5, 1970 Appl. No.: 16,735

Foreign Application Priority Data Mar. 10, 1969 France ..6906642 U.S.Cl123/32 EA, 123/1191 123/140 MC Int. Cl ..F02m 51/00 Field Of Search..l23/32, 32 EA, 32 AB, 119, 123/139 E JL U Guiot ..l23/32 EA Scholl..l23/32 EA Primary Examiner- Laurence M. Goodridge Attorneyl(enyon &Kenyon Reilly Carr & Chapin [57] ABSTRACT An electronic circuit systemfor triggering the successive injectors of an internal combustionengine, chiefly a Diesel engine. A first circuit controlled by therotation of the engine provides for the starting of saw-tooth voltagewave, the length of the rising slope of which depends on the speed ofrotation while the peals of said pulses trigger the injections whichlast until the end of the pulse. A delay for said triggering isadvantageously obtained by the difference between the time constants oftwo flip-flops the first of which is constant while that of the secondflip-flop depends on the operative parameters of the engine, the end ofthe injection being defined by the end of the signal produced by thefirst flip-flop.

9 Claims, 5 Drawing Figures PATENTEDAPR 41972 3,653,365

sum 2 or 3 1? T TOR/VEYS ELECTRONIC CONTROL SYSTEM FOR THE INJECTORS OFINTERNAL ENGINES The present invention has for its object an arrangementfor electronically controlling injectors in internal combustion engineswherein each injection is triggered by a pulse generator controlled bythe rotation of the engine.

In order to obtain a satisfactory operation of an engine, whether it isequipped with mechanically controlled injectors or, as in the case ofthe present invention, with electronically controlled injectors, it isoften necessary to obtain a modification in the starting point of theinjection depending on the speed of rotation of the engine and/or on theload. It has previously been proposed to modify said starting point inaccordance with the speed of rotation by centrifugally controlled meansfor mechanically as for electronically controlled injections. Withelectronically controlled injectors, voltage generators have previouslybeen used, operating as a function of said speed of rotation, thevoltage obtained defining a lag for the injection with reference to asignal produced by a pulse generator associated with the rotation of theengine, which lag diminishes with an increase of the speed of rotation;said pulse generator is designed in a manner such that the lag becomeszero for a maximum speed of rotation, that is the lead of the injectionwith reference to the upper idle center becomes a maximum. By providingfurthermore a control of the beginning of the injection by the load, itis possible to adjust the injection in accordance with the requirementsof each engine.

Although such an arrangement is only of slight interest for sparkcontrolled ignition engines in association with an indirect injection,it becomes essential in the case of Diesel engines since in this casethe beginning of the combustion is defined by the beginning of theinjection, taking into account the delay required for ignition inaccordance with physical and chemical conditions and also with thegeometrical structure of the engine.

The above-mentioned devices are however somewhat bulky and subject towear as is the case with all mechanical or electromechanicalarrangements.

The present invention has for its object to eliminate said drawbacks andit has more particularly for its object an electronic control system forthe injectors of internal combustion engines, wherein the injection istriggered by a pulse generator controlled by the rotation of the engine.According to the present invention there is obtained a lag for theinjection by means of electronic delaying means controlled by the rotaryspeed of the engine, said means including a circuit generating asaw-tooth voltage the rise of which is triggered by pulses fed by saidpulse generator while its peak triggers an injector, the slope of saidsaw-tooth voltage being such that, according to the spacing in time ofthe generated pulses, that is according to the rotary speed of theengine, the spacing between the peaks and troughs of said saw-toothvoltage is reduced together with the lag of the injection when therotary speed increases. Complementary electronic delay means may be provided which operates under the control of the engine load of the engineand which includes two flip-flops triggered simultaneously by a signalcontrolled directly or indirectly by the rotation of the engine. Thefirst flip-flop produces a rectangular signal of a constant durationwhile the second flip-flop produces a rectangular signal the duration ofwhich varies with the load of the engine. The flip-flops act on a commoncircuit designed in a manner such that it produces a rectangular signalfor controlling the injection, the duration of which is equal to thedifference between the durations of the signals produced by said firstand second flip-flops. The injection begins at the end of the signalproduced by the second flip-flop and ends together with the signalproduced by the first flipflo l y way of example and in order to furtherthe understanding of the description, the accompanying drawings areprovided in which:

FIG. 1 is a block diagram of the arrangement according to the invention;

FIG. 2 sets forth graphs showing the succession of signals produced bythe different sections of the arrangement illustrated in FIG. 1; and

FIG. 3 is a schematic diagram of an electronic circuit executed inconformity with the invention.

FIG. 4 illustrates the succession of signals produced by the differentsections of the arrangement illustrated in FIG. 1 corresponding to onevalue of rotary speed of the engine.

FIG. 5 illustrates the succession of signals produced by the differentsections of the arrangement illustrated in FIG. 1 corresponding to ahigher value of rotary speed of the engine than illustrated in FIG. 4.

As illustrated in FIG. 1, pulse generator A controlled by the rotationof the engine, which is not illustrated, sends a pulse to the saw-toothvoltage generator B, said saw-tooth voltage being transformed at C intopositive rectangular signals which are cut off during a period To (FIG.2) each time a pulse is applied to the saw-tooth generator B and whichstart at each peak of the saw-tooth voltage. The circuit Csimultaneously triggers flip-flops D and E each time it produces arectangular signal. The flip-flop D produces a rectangular signal ofconstant duration T1, while the flip-flop E produces a rectangularsignal of duration T2, the length of which depends on various operativeparameters of the engine which parameters are transmitted through thesensors a,b and c. The flip-flop signals T1 and T2 are applied to acommon circuit F producing a rectangular signal for controlling theinjection and the duration of which, T, is equal to the difference T1-T2defining the duration of injection. Said signal of duration T istransmitted to a circuit G distributing the signals T into the injectorsH in accordance with the predetermined order of injection.

FIG. 2 illustrates the various signals produced by the successiveelementary circuits of FIG. 1. The pulse A produces transient pulses thespacing of which depends on the rotary speed of the engine. The pulsesillustrated in interrupted lines correspond to a higher speed ofrotation, which means a shorter interval between successive pulses. Eachpulse triggers saw-tooth voltage generator B. Said saw-tooth voltagepulses increase linearly during a period To until a well-defined peakvalue is obtained. At this moment, the circuit C begins producing arectangular signal To and the voltage produced by the generator Bdecreases linearly until the next pulse received from pulse generator Acuts off the rectangular signal produced by the circuit C.

As illustrated in dotted lines, the interval between two successivepulses decreases when the rotary speed increases. Consequently thesaw-tooth voltages cannot decrease as far as far lower speeds. Thus, theduration To, is shorter, since the peak of the saw-tooth voltages doesnot vary. The duration To corresponds to the lag required for injectionas a function of the speed of rotation, with reference to the pulseproduced by the generator A. This lag decreases rapidly for increasingspeeds by the shortening of the rising and falling slopes of thesaw-tooth voltage.

Since the pulses produced by the pulse generator A are obtained clearlybefore the upper idle centers of the engine pistons, the circuits B andC produce signals which lead with reference to the upper idle centers,the lead measured by the rotary angle travelled over by the crankshaftvarying with the speed of rotation in accordance with the lengths of thevoltage slopes.

It should be noted that is is possible to utilize only to the circuits Band C with an electronic injection-controlling system when it is merelydesired to time the injections under the control of the speed ofrotation.

However and more particularly in the case of Diesel engines, it is oftenof interest, for a given speed of rotation, to end the injection at apredetermined time, whatever may be the duration of the injection, thatis whatever may be the amount of fuel to be injected. To obtain such aresult, the invention utilizes two flip-flops, D and E, as mentionedhereinabove. The first flip-flop D produces a rectangular signal ofconstant duration T1 while the second flip-flop E produces a rectangularsignal of variable duration T2. The circuit F fed by both flip-flopsproduces a rectangular injectioncontrolling signal of a duration T=T1T2,the beginning of which coincides with the end of the second rectangularsignal of duration T2, while its end is controlled by the end of thefirst rectangular signal of duration Tl. It is thus apparent that withthe arrangement according to the invention, there is obtained a lag ofthe injection with reference to the triggering pulse produced by thepulse generator A, equal to 70+72. To

depends on the speed of rotation while T2 is a function of the load onthe engine.

The injection lag T plus T2 is illustrated in FIGS. 4 and 5. T0 variesas a function of the rotary speed of the engine, and T2 varies as afunction of the load on the engine. Referring to FIG. 4, a series oftiming pulses having a predetermined frequency which corresponds to onerotary speed of the engine, are illustrated on line A. FIG. illustratesa corresponding series of timing pulses (line A) having a predeterminedfrequency of about twice the frequency of the pulses illustrated in FIG.4, thus representing the increase in the rotary speed of the engine. Asshown in FIGS. 4 and 5, each timing pulse triggers the saw tooth voltagegenerator which generates the saw-tooth voltage illustrated on lines Band B. The peak of the saw-tooth voltage does not vary. Thus, bycomparing the respective saw tooth voltages of FIGS. 4 and 5, it can beseen that the rise time for the respective saw-tooth voltages decreasesas the frequency of the pulses increases, corresponding to an increasein the rotary speed of the engine. The rise time of the saw-toothvoltages is represented by 70 and T'O, respectively.

The first rectangular pulse generating means D and the secondrectangular pulse generating means E are triggered each time the sawtooth voltage reaches its peak. The first rectangular pulse generated bythe first generating means has a predetermined duration represented inFIGS. 4 and 5 by T1 and T 1, respectively. The second rectangular pulsegenerated by the second generating means has a duration which varies asa function of at least one engine parameter such as the load on theengine. These durations are represented by T2 and T2, respectively. Thedurations 72 and T2 are shown as being unequal, thus corresponding tothe different loads on the engine. As the load on the engine decreases,the time T2 decreases.

Referring to line F of FIG. 4, the actuating pulse, having a durationrepresented by T, beings at a variable time interval equal to T0 plus T2after each timing pulse generated by the pulse generator, and theactuating pulse ceases at the end of the first rectangular pulse fromthe first generator means which has a fixed width or duration T1. Thetime 70 is variable and is determined by the frequency of the timingpulses generated by the pulse generator, which is a function of therotary speed of the engine. As noted above, the time T2 varies as afunction of at least one of the engine parameters such as the load onthe engine. Thus, the ignition lag or elapsed time 70 plus 72 betweeneach timing pulse of the pulse generator and the corresponding actuatingpulse, having a duration T, is a function of both the rotary speed ofthe engine and the load on the engine. This can be clearly seen bycomparing the ignition lag of FIG. 4 with the ignition lag TO plus T2illustrated in FIG. 5. Also, the duration of the actuating pulse, T andT, respectively, increases as the load in the engine increases, since T2and T2 are decreasing.

FIG. 3 illustrates the electronic circuit incorporating the circuitsB,C,D,E and F shown in block diagram in FIG. 1. The saw-tooth voltagegenerator B comprises a program-controllable uni-junction transistor T2and a condenser 3 charged under constant current conditions through aresistance 17, a transistor TI and a diode 19, while it is dischargedunder constant current conditions through the transistor T8 and theresistance 20. The base of the transistor T1 is maintained at apredetermined adjustable voltage by a voltage-divider constituted by theresistances 5 and 7 connected by a potentiometer 6, while the electrodecontrolling the uni-junction transistor T2 is maintained at anothervoltage defined by a voltage-divider comprising series resistances 15and 16. The point connecting the anodes of the diode 19 and of theprogram-controllable uni-junction transistor T2 with the collector ofthe transistor TI is grounded through the collector-emitter circuit ofthe transistor T4 while the base of transistor T4 forms the input E ofthe saw-tooth voltage generator to which the signal produced by thepulse generator A is applied. Said input E is grounded through theresistance 23. The control electrode of the uni-junction transistor T2is connected with the base of another transistor T10 through aresistance 25 forming part of the voltage-divider constituted by theresistances 27, 26, 25 and 24. The collector-emitter circuit of saidtransistor T10 is connected in parallel with a condenser 11 between thepoint connecting further resistances 21 and 22 and ground. Theresistances 21 and 22 form with a grounded potentiometer 9 a furthervoltage-divider, the slider of said potentiometer 9 defining the voltageapplied to the base of the transistor T8 so that said voltage may assumea predetermined adjustable value.

The circuit C includes transistor T12 the emitter-collector circuit ofwhich is connected in series with the resistance 28 between the supplyof voltage and ground, while its base is connected with the pointconnecting the resistances 26 and 27. The collector of the transistorT12 forms the output S of the circuit C. The output signals aretransmitted through the diode 29, the condenser 31 and diode 32 toflip-flop E and diode 33 to flip-flop D. In order to discharge thecondenser 31 after a positive signal has charged it, the pointconnecting the diode 29 with said condenser 31 is grounded through aresistance 30.

The flip-flops E and D each comprises a program-controllableuni-junction transistor, T37 or T49 connected in series with variableresistance 38 and with fixed resistance 48, respectively. The cathodesof said program-controllable unijunction transistors are connected withthe bases of the corresponding transistors T41 and T52. The pointsconnecting the resistances 38 and 48 with the anodes of the uni-junctiontransistors T37 and T49 are grounded respectively through thecollector-emitter circuits of the corresponding transistors T34 and T46and through the corresponding condensers 36 and 47 in parallel with thelatter. The bases of the transistors T34 and T46 are grounded throughthe resistances 35 and 45 respectively and are connected with thecathodes of the corresponding diodes 32 and 33 fed by the circuit Cthrough the condenser 31. The electrodes controlling said uni-junctiontransistors T37 and T46 are maintained at a predetermined voltage by thevoltage-dividers constituted respectively by the series resistances39-40 and 50-51.

The circuit F producing the rectangular injection-controlling signals isconstituted by the transistors T41 and T52, already referred to asconnected through their bases with the cathodes of the correspondingprogramme-controllable unijunction transistors T37 and T49. Thecollector-emitter circuit of each of said transistors T41 and T52 isconnected in series with the corresponding resistances 42 or 53. betweenthe voltage supply and ground. A connection between the collector of thetransistor T41 and the base of the transistor T52 is provided through adiode 43 and a resistance 44. The point connecting the collector of thetransistor T52 with the corresponding resistance 53 forms the output Sfor the rectangular signal controlling the injection and the duration ofwhich is T.

The operation of the circuit is as follows:

When the voltage supply is applied and in the absence of any signal atthe input E of saw-tooth voltage generator B, the programme-controllableuni-junction transistor T2 is conductive and is fed with a current thevalve of which is defined by the resistance 17 and the conductance oftransistor T1, as a function of the voltage applied to the base of saidtransistor T1. The anode and the control electrode of the uni-junctiontransistor T2 are substantially at zero voltage so that no charge can beapplied to the condenser 3. Similarly, the point connecting T8resistances 25 and 26 is practically at zero voltage whereby thetransistor T12 remains conductive. However, by reason of the presence ofthe condenser 31, this has no influence on the flip-flops D and E. Thepoint connecting said resistances 25 and 26 being at zero voltage,transistor T is nonconductive and a predetermined voltage is applied tothe base of transistor T8 as defined by the voltage-divider constitutedby the resistances 21 and 22 and by the position of the slider of thepotentiometer 9. This results in transistor T3 conducting and condenser3 remains in a discharged condition.

As to the flip-flops E and D, the uni-junction transistors T37 and T49are conductive since the transistors T34 and T46 are non-conductive,while the condensers 36 and 47 are discharged and the electrodescontrolling said program-controllable single-junction transistors T37and T49 are subjected to a voltage which is substantially equal to zero.Consequently,

and the transistor T52 is cut off. When T52 is cut off the output at Srises sharply to a value determined by resistance 53 and the voltagesupply. The output S remains at this voltage until T52 conducts again.This occurs at the end of the pulse of duration Tl, when T49 and T52conduct. The result is that a rectangular signal of a duration T equalto Tl T2 appears at the transistors T41 and T52 are both conductive sothat the output S of the circuit F is substantially at zero voltage,

If a short pulse is now applied at the input E of the saw-tooth voltagegenerator B, transistor T4 becomes momentarily conductive and thevoltage applied to the anode of the transistor T2is returnedsubstantially to Zero and said transistor T2 is cut off. When the pulseapplied to the input E terminates, the transistor T4 is nonconductiveagain and a constant charging current is established, as defined by theresistance 17 and the conductive transistor T1 whereby the voltage onthe anode of the uni-junction transistor T2 rises linearly. During thistime, the control electrode of said uni-junction transistor T2 is at toa voltage defined by the voltage divider constituted by the resistancesl5 and 16, said voltage also being applied simultaneously to the base ofthe transistor T10 making it conductive. This results in the voltage atthe point connecting resistances 21 and 22 and on the base of transistorT8 becoming zero. Transistor T8 is then cut off. The transistor T12 isalso cut off by the voltage applied to its base and the voltage at theoutput S of the circuit C is returned to zero, this having however noeffect on the flip-flops D and E.

When the voltage across the terminals of the condenser 3 reaches apredetermined value, depending on the voltage applied to the controlelectrode ofthe uni-junction transistor T2, the latter again suddenlybecomes conductive. At this moment, the voltage on the control electrodeof the transistor T2 becomes substantially zero and the transistor T12again becomes conductive while transistor T10 is again cut off.Consequently, condenser 11 is charged and the voltage applied to thebase of transistor T8 rises so that said transistor T8 becomesconductive. Therefore, during the period during which the transistor T10is cut off, and transistor T8 is conductive condenser 3 is dischargedunder constant current conditions through the transistor T8 and theresistance 20. The diode 19 prevents any discharge through theuni-junction transistor T2 or through the transistor T4. The dischargeof the condenser 3 continues until a further pulse appears at the inputE ofcircuit B.

At the moment at which the transistor T12 again becomes conductive, apositive pulse is transmitted to the bases of the transistors T34 andT46 through the diode 29, the condenser 31 and the corresponding diodes32 and 33. Said transistors T34 and T46 then become momentarilyconductive, which results in a return to zero of the voltage applied onthe anodes of the uni-junction transistors T37 and T49 which are thuscut off. From this moment, condensers 36 and 4'7 are charged accordingto a time constant defined by their capacities and by the values of theresistances 38 and 48. The uni-junction transistors T37 and T49 beingcut off, the transistor T41 is also cut off and this causes a voltage tobe applied to the base of transistor T52 which is held in a conductivecondition so that the output S of the circuit F is at zero voltage.However, since the time constants T1 and T2 of the flip-flops D and Eare selected so that T1 is larger than or equal to T2, the transistorT37 becomes conductive before the transistor T49. When T37 becomesconductive, T41 will become conductive. At this moment, the pointconnecting the resistance 42 with the collector of the transistor T41.is returned to zero voltage the output S of the circuit F.

The time constant of each of the flip-flops E and D is defined by thecapacities of the condensers 36 and 47 and by the values of theresistances 38 and 48.

As a matter of fact, as long as the programme-controllable uni-junctiontransistors T37 and T49 are cut off, condensers 36 and 47 are beingcharged, but as soon as the voltage across the said condensers 36 and 47reaches a predetermined value, defined by the voltage applied to theelectrodes controlling the corresponding uni-junction transistors T37and T49, the latter suddenly conduct and cause transistor T41 and T52 toconduct, the injection-controlling signal at S returning to zero voltageas soon as transistor T52 again becomes.

This therefore produces a duration of the injection-controlling signalwhich is equal to T=TlT2 and its value may range between T=O and T=T1.The modification in the duration of injection is obtained by amodification of T2 provided by the variable resistance 38 under controlof the load on the engine, the timing of the end of the injection periodremaining constant for a predetermined speed of rotation.

Turning to the saw-tooth voltage generator B, its cycle loading anddischarging the condenser 3 is defined by the pulses applied to theinput E. Now, since the slope of the rising voltage is defined by thecurrent passing through the transistor T1, that is by the voltageapplied to the base of the latter, while the slope of the fallingvoltage is defined by the current passing through transistor T8, that isby the voltage applied to the base of the latter, the time available forthe charging and discharging is obviously shortened when the speed ofrotation increases. Consequently, the difference between the eaks andtroughs of the saw-tooth voltage decreases gradually with increasingspeeds since, the duration of discharge of the condenser 3 decreasessteadily. Therefore, the time T0 elapsing from the moment of theapplication of the signal at the input E for charging the condenser 3 upto the peak of the saw-tooth voltage decreases when the speed ofrotation increases. Consequently the duration To is a function of thespeed of rotation and according to the voltage slopes defining thecharging and discharging of condenser 3, the time To decreases rapidlywith an increase in the speed of rotation. Since the angle 0 measured indegrees defining the angular travel of the crankshaft beginning at themoment of the pulse produced by the pulse generator A and terminating atthe end of the period To is directly proportional to the rotary speed Nof the engine and is inversely proportional to said duration To, thefollowing equation is true:

P being a coefficient of proportionality. Therefore, it is possible toselect the slopes of the saw-tooth voltage in a manner such that 0increases with the speed of rotation, remains constant when said speedis constant and decreases with said speed, this being of major interestsince it corresponds to an increase of the lead with reference to theupper idle center when the rotary speed increases.

It should also be noted that the control electrode of theprogram-controllable uni-junction transistor 12 may be connecteddirectly with the point joining the resistances 21 and 22, andtransistor T10 and condenser 11 eliminated.

In such a case, the condenser 3 begins its discharge as soon as apositive voltage appears. In contradistinction, if transistor T10 andcondenser 11 are retained, transistor T8 becomes conductive only afterthe charging of condenser 11. The latter case corresponds to FIG. 2,assuming a horizontal line extends across the rising and falling slopesof the saw-tooth voltage waves so as to separate said slopes.

it is therefore obvious that with simple static circuits having nomoving parts, it is possible to obtain an arrangement providing anadjustment of the delay of the injection with reference to apredetermined position of the crankshaft under control of the rotaryspeed and also control delay of the injection in accordance with theload on the engine, both adjustments being readily executed by means ofpotentiometers so as to take into account the type of engineincorporating the arrangement described.

I claim:

1. An electronic control system for electromagnetic fuel injectors in aninternal combustion engine, comprising:

a. a pulse generator for generating timing pulses spaced as a functionof the rotary speed of the engine, the spacing between the timing pulsesdecreasing as speed increases;

b. a saw tooth voltage generator for generating a saw tooth voltage inresponse to each of said pulses, the duration of said saw tooth voltagebeing dependent on the spacing between successive timing pulses, thetime interval between each timing pulse and the peak voltage of the sawtooth voltage generated in response to the timing pulse being a functionof the rotary speed of the engine, and

. means triggered by the peak voltage of each of said saw tooth voltagesfor producing actuating pulses for said electromagnetic injectors,whereby the time interval between a pulse generated by said pulsegenerator and the actuating pulse triggered by the peak voltage of thesaw tooth voltage generated in response to the pulse is a function ofthe rotary speed ofsaid engine.

2. The electronic control system set forth in claim 1 wherein said meansfor producing actuating pulses comprises:

a. first rectangular pulse generating means for generating firstrectangular pulses of predetermined width;

b. second rectangular pulse generating means for generating secondrectangular pulses the widths of which vary as a function of at leastone engine parameter such as the load on the engine;

c. means for simultaneously triggering said first and second rectangularpulse generating means in response to the peak voltage of each of saidsaw tooth voltages; and

d. means for combining the outputs of said first and second rectangularpulse generating means for producing rectangular actuating pulses equalin width to the difference between the width of the first rectangularpulse and the width of the second rectangular pulse, each of saidactuating pulses commencing at the end of each second rectangular pulsefrom said second rectangular pulse generating means and ending at theend of each first rectangular pulse from said first rectangular pulsegenerating means, whereby the time interval between a timing pulsegenerated by said pulse generator and the beginning of the actuatingpulse corresponding to the timing pulse is a function of the rotaryspeed of the engine and the engine parameter, and the width of theactuating pulse is a function of the engine parameter.

3. A system as claimed in claim 2 wherein said saw-tooth voltagegenerator includes a condenser, a circuit for charging the condenserwith an adjustable constant current, a circuit for discharging thecondenser under adjustable constant current conditions, a programmableuni-junction transistor connected in parallel with said condenser andthe control electrode of which is connected with the condenserdischarging circuit, a voltage divider feeding said control electrodeand adapted to render simultaneously conductive said uni-junctiontransistor and said condenser discharging circuit, the charging of thecondenser being started by a pulse from said pulse generator renderingsaid uni-junction transmission nonconductive.

4. A system as claimed in claim 2 wherein said saw-tooth voltagegenerator includes a condenser, a circuit for charging the condenserwith an adjustable constant current, a circuit for discharging thecondenser under adjustable constant current conditions, a programmableuni-junction transistor connected in parallel with said condenser andthe control electrode of which is connected with the condenserdischarging circuit, a voltage divider feeding said control electrodeand adapted to render simultaneously conductive said uni-junctiontransistor and the condenser discharging circuit, a primary transistorconnected between the anode of the uni-junction transistor and groundand the base of which is connected with the pulse generator whereby itbecomes momentarily conductive each time a pulse is applied to said baseand the voltage applied to the anode of said uni-junction transistor ismomentarily returned to zero so that said uni-junction transistor is cutoff while the condenser begins its charging period.

5, A system as claimed in claim 2 wherein said saw-tooth voltagegenerator includes a condenser, a circuit for charging said condenserwith an adjustable constant current, a circuit for discharging saidcondenser under adjustable constant current conditions, a programmableuni-junction transistor connected in parallelwith said condenser and thecontrol electrode of which is connected with said condenser-dischargingcircuit, a voltage-divider feeding said control electrode and adapted torender simultaneously conductive said uni-junction transistor and saidcondenser-discharging circuit, the charging of said condenser beingstarted by a pulse from said pulse generator cutting off saiduni-junction transistor, a voltage divider defining the current in saidcondenser charging circuit, a further transistor the collector of whichis connected with a point of said voltage divider, the emitter of whichis grounded and the base of which is connected with the controlelectrode of said uni-junction transistor whereby said furthertransistor is conductive when said uni-junction transistor is cut offand is non-conductive when said uni-junction transistor is conducting, afurther condenser connected in parallel with the emittercollectorcircuit of said further transistor whereby a lag is obtained between thecutting off of said further transistor and the moment at which saidcondenser-discharging circuit becomes conductive,

6. A system as claimed in claim 2 wherein said saw-tooth voltagegenerator includes a condenser, a circuit for charging the condenserwith an adjustable constant current, a circuit for discharging thecondenser under adjustable constant current conditions, a programmableuni-junction transistor connected in parallel with said condenser andthe control electrode of which is connected with said condenserdischarging circuit, a voltage divider feeding said control electrodeand adapted to render simultaneously conductive said uni-junctiontransistor and the condenser-discharging circuit, the charging of saidcondenser being started by a pulse from said pulse generator cutting offsaid uni-junction transistor, a voltage-divider defining the current insaid condenser-charging circuit, a further transistor the collector ofwhich is connected with a point of said voltage-divider, the emitter ofwhich is grounded and the base of which is connected with the controlelectrode of said uni-junction transistor whereby said furthertransistor is conductive when said uni-junction transistor is cut offand is non-conductive when said uni-junction transistor is conductive, afurther condenser connected in parallel with the emitter-collectorcircuit of said further transistor whereby a lag is obtained between thecutoff of said further transistor and the moment at which thecondenser-discharging circuit becomes conductive, a grounded resistance,a still further transistor the emitter-collector of which is connectedbetween the voltage supply and said grounded resistance and the base ofwhich is connected with the control electrode of said unijunctiontransistor, the point connecting said grounded resistance and said stillfurther transistor being connected with said first and secondrectangular pulse generating means to feed them with the rectangularsignal passing through said point as long as said uni-junctiontransistor is conductive.

7. A system as claimed in claim 2 wherein said first and secondrectangular pulse generating means comprise respectively first andsecond flip-flops and said combining means includes a first and a secondauxiliary transistor the bases of which are respectively connected withsaid first and second flip-flops, a resistance connected in theemitter-collector circuit of each auxiliary transistor, means foradjusting the time constant of said second flip-flop between zero andthe value of the time constant of said first flip-flop, a diodeconnecting the collector of the auxiliary transistor connected with thesecond flip-flop, with the base of the auxiliary transistor connectedwith the first flip-flop and a connection adapted to tap said actuatingpulses for the injectors off the collector of the auxiliary transistorconnected with said first flip-flop.

8. A system as claimed in claim 7 wherein a programmable uni-junctiontransistor and a resistance connected in series between the voltagesupply and the base of its associated auxiliary transistor,voltage-divider means for maintaining a predetermined voltage on thecontrol electrode of said unijunction transistor, a condenser, a furtherauxiliary transistor the emitter-collector circuit of which is connectedin parallel with said condenser between the anode of said uni-junctiontransistor and ground and the base of which is connected to said meansfor simultaneously triggering, so as to return to zero the voltage onthe anode of said uni-junction transistor and thereby trigger saidflip-flop, which returns to its initial condition when the voltage onsaid condenser reaches a value with reference to that on the controlelectrode of said uni- 0 junction transistor to render it conductive.

9. A system as claimed in claim 7 further including a diode and acondenser connected in series between said means for simultaneouslytriggering and said flip-flops.

1. An electronic control system for electromagnetic fuel injectors in aninternal combustion engine, comprising: a. a pulse generator forgenerating timing pulses spaced as a function of the rotary speed of theengine, the spacing between the timing pulses decreasing as speedincreases; b. a saw tooth voltage generator for generating a saw toothvoltage in response to each of said pulses, the duration of said sawtooth voltage being dependent on the spacing between successive timingpulses, the time interval between each timing pulse and the peak voltageof the saw tooth voltage generated in response to the timing pulse beinga function of the rotary speed of the engine, and c. means triggered bythe peak voltage of each of said saw tooth voltages for producingactuating pulses for said electromagnetic injectors, whereby the timeinterval between a pulse generated by said pulse generator and theactuating pulse triggered by the peak voltage of the saw tooth voltagegenerated in response to the pulse is a function of the rotary speed ofsaid engine.
 2. The electronic control system set forth in claim 1wherein said means for producing actuating pulses comprises: a. firstrectangular pulse generating means for generating first rectangularpulses of predetermined width; b. second rectangular pulse generatingmeans for generating second rectangular pulses the widths of which varyas a function of at least one engine parameter such as the load on theengine; c. means for simultaneously triggering said first and secondrectangular pulse generating means in response to the peak voltage ofeach of said saw tooth voltages; and d. means for combining the outputsof said first and second rectangular pulse generating means forproducing rectangular actuating pulses equal in width to the differencebetween the width of the first rectangular pulse and the width of thesecond rectangular pulse, each of said actuating pulses commencing atthe end of each second rectangular pulse from said second rectangularpulse generating means and ending at the end of each first rectangularpulse from said first rectangular pulse generating means, whereby thetime interval between a timing pulse generated by said pulse generatorand the beginning of the actuating pulse corresponding to the timingpulse is a function of the rotary speed of the engine and the engineparameter, and the width of the actuating pulse is a function of theengine parameter.
 3. A system as claimed in claim 2 wherein saidsaw-tooth voltage generator includes a condenser, a circuit for chargingthe condenser with an adjustable constant current, a circuit fordischarging the condenser under adjustable constant current conditions,a programmable uni-junction transistor connected in parallel with saidcondenser and the control electrode of which is connected with thecondenser discharging circuit, a voltage divider feeding said controlelectrode and adapted to render simultaneously conductive saiduni-junction transistor and said condenser discharging circuit, thecharging of the condenser being started by a pulse from said pulsegenerator rendering said uni-junction transmission nonconductive.
 4. Asystem as claimed in claim 2 wherein said saw-tooth voltage generatorincludes a condenser, a circuit for charging the condenser with anadjustable constant current, a circuit for discharging the condenserunder adjustable constant current conditions, a programmableuni-junction transistor connected in parallel with said condenser andtHe control electrode of which is connected with the condenserdischarging circuit, a voltage divider feeding said control electrodeand adapted to render simultaneously conductive said uni-junctiontransistor and the condenser discharging circuit, a primary transistorconnected between the anode of the uni-junction transistor and groundand the base of which is connected with the pulse generator whereby itbecomes momentarily conductive each time a pulse is applied to said baseand the voltage applied to the anode of said uni-junction transistor ismomentarily returned to zero so that said uni-junction transistor is cutoff while the condenser begins its charging period.
 5. A system asclaimed in claim 2 wherein said saw-tooth voltage generator includes acondenser, a circuit for charging said condenser with an adjustableconstant current, a circuit for discharging said condenser underadjustable constant current conditions, a programmable uni-junctiontransistor connected in parallel with said condenser and the controlelectrode of which is connected with said condenser-discharging circuit,a voltage-divider feeding said control electrode and adapted to rendersimultaneously conductive said uni-junction transistor and saidcondenser-discharging circuit, the charging of said condenser beingstarted by a pulse from said pulse generator cutting off saiduni-junction transistor, a voltage divider defining the current in saidcondenser charging circuit, a further transistor the collector of whichis connected with a point of said voltage divider, the emitter of whichis grounded and the base of which is connected with the controlelectrode of said uni-junction transistor whereby said furthertransistor is conductive when said uni-junction transistor is cut offand is non-conductive when said uni-junction transistor is conducting, afurther condenser connected in parallel with the emitter-collectorcircuit of said further transistor whereby a lag is obtained between thecutting off of said further transistor and the moment at which saidcondenser-discharging circuit becomes conductive.
 6. A system as claimedin claim 2 wherein said saw-tooth voltage generator includes acondenser, a circuit for charging the condenser with an adjustableconstant current, a circuit for discharging the condenser underadjustable constant current conditions, a programmable uni-junctiontransistor connected in parallel with said condenser and the controlelectrode of which is connected with said condenser discharging circuit,a voltage divider feeding said control electrode and adapted to rendersimultaneously conductive said uni-junction transistor and thecondenser-discharging circuit, the charging of said condenser beingstarted by a pulse from said pulse generator cutting off saiduni-junction transistor, a voltage-divider defining the current in saidcondenser-charging circuit, a further transistor the collector of whichis connected with a point of said voltage-divider, the emitter of whichis grounded and the base of which is connected with the controlelectrode of said uni-junction transistor whereby said furthertransistor is conductive when said uni-junction transistor is cut offand is non-conductive when said uni-junction transistor is conductive, afurther condenser connected in parallel with the emitter-collectorcircuit of said further transistor whereby a lag is obtained between thecutoff of said further transistor and the moment at which thecondenser-discharging circuit becomes conductive, a grounded resistance,a still further transistor the emitter-collector of which is connectedbetween the voltage supply and said grounded resistance and the base ofwhich is connected with the control electrode of said uni-junctiontransistor, the point connecting said grounded resistance and said stillfurther transistor being connected with said first and secondrectangular pulse generating means to feed them with the rectangularsignal passing through said point as long as said uni-junctiontraNsistor is conductive.
 7. A system as claimed in claim 2 wherein saidfirst and second rectangular pulse generating means compriserespectively first and second flip-flops and said combining meansincludes a first and a second auxiliary transistor the bases of whichare respectively connected with said first and second flip-flops, aresistance connected in the emitter-collector circuit of each auxiliarytransistor, means for adjusting the time constant of said secondflip-flop between zero and the value of the time constant of said firstflip-flop, a diode connecting the collector of the auxiliary transistorconnected with the second flip-flop, with the base of the auxiliarytransistor connected with the first flip-flop and a connection adaptedto tap said actuating pulses for the injectors off the collector of theauxiliary transistor connected with said first flip-flop.
 8. A system asclaimed in claim 7 wherein a programmable uni-junction transistor and aresistance connected in series between the voltage supply and the baseof its associated auxiliary transistor, voltage-divider means formaintaining a predetermined voltage on the control electrode of saiduni-junction transistor, a condenser, a further auxiliary transistor theemitter-collector circuit of which is connected in parallel with saidcondenser between the anode of said uni-junction transistor and groundand the base of which is connected to said means for simultaneouslytriggering, so as to return to zero the voltage on the anode of saiduni-junction transistor and thereby trigger said flip-flop, whichreturns to its initial condition when the voltage on said condenserreaches a value with reference to that on the control electrode of saiduni-junction transistor to render it conductive.
 9. A system as claimedin claim 7 further including a diode and a condenser connected in seriesbetween said means for simultaneously triggering and said flip-flops.